PROJECT SUMMARY Lesbian, gay, bisexual, queer and other sexual minority youth (SMY) are at greater risk than their heterosexual counterparts for suicidal thoughts and behaviors (STB), nonsuicidal self-injury (NSSI), and myriad health problems. Specifically, SMY endorse both STB and NSSI at rates 3 times greater than heterosexual youth. NSSI, while a major public health concern in its own right, significantly exacerbates risk for suicidal behavior. Thus, examining suicidal and self-injurious behaviors among SMY is a federal public health priority, as acknowledged by NIH PA-15-263. The psychological mediation framework, an adaptation of the minority stress (MS) model, posits that MS (i.e., stressors ranging from daily slights or insults to more overt forms of bullying and discrimination related to marginalized sexual orientation) leads to impaired general psychological processes, such as emotional dysregulation, maladaptive cognitive processes, and social and interpersonal difficulties, as well as sexual minority group-specific processes (e.g., internalized homophobia).Consequently, these processes put SMY at increased risk for psychopathology. The proposed research seeks to address gaps in the field by examining potential mechanisms that may account for the relationship between MS and STB/NSSI in SMY. Informed by the psychological mediation framework as well as our own pilot research findings, we seek to investigate mechanisms across four areas of functioning: affective (affect intensity, affect dysregulation, rumination, and attention bias to negative affect), cognitive (low self-esteem), interpersonal (insufficient social support and interpersonal rejection sensitivity) and sexual minority-group specific (internalized homophobia and sexual orientation concealment). Very importantly, each of these hypothesized mechanisms have been found to be associated with increased risk for suicidality, and each represent potential targets of intervention. We propose an innovative exploratory study, administering subjective self-report measures and objective behavioral tasks to high risk SMY (N=60), recruited from various clinical settings. We will examine whether MS is associated with specific affective, cognitive, interpersonal, and group-specific mechanisms, and whether these are in turn associated with STB/NSSI in SMY (Aim 1). Using a daily diary approach, we will examine the extent to which hypothesized these mechanisms account for the relationship between MS and STB/NSSI in their natural environment (Aim 2). We will also conduct Timeline Followback interviews with all participants at the end of the daily diary phase. To inform the development of future interventions, we also propose conducting in-depth interviews with an at-risk subset of the same SMY participants (n=20) to better understand their experiences with these mechanisms, coping, and treatment. Findings from this study would demonstrate feasibility for a larger-scale, prospective R01 study to elucidate the mechanisms underlying the increased risk for NSSI/STB in SMY and pilot data to develop effective and culturally-sensitive interventions.